Compressor



Nov..22, 193s. .A. D. ERGUSON 2,137,752

COMPRESSOR Filed May 2, 1935 -3nventor (Ittorneg Patented Nov; 22,

oomaassoa Alexander D. Ferguson, Michigan City, -Ind.,'- assignorto Sullivan Machinery Company, a notation oi. Massachusetts Application May 2, 1935, Serial No. 19,455

'24 Claims.

invention relatesto compressors, and more particularly to improved controlling. means for elfecting unloading, in the desired manner, of

compound compressors.

pressed fluid in the intercooler may be compressed in the high pressure cylinder and discharge to the dischargeline, thereby effecting a small, but desirable, economy. After complete unloading is effected, there is a tendency for the intercooler pressure gradually to buildup, due to-leakage past the intake unloader valve and the absence,

due to the holding open of the inlet valves oithe high pressure cylinder, of continuous removal of air from the intercooler by. the high pressure cylinder; andtherefore there is likely to be a periodic popping of the safety valve which is provided on the intercooler, a thing which is an- I noying, and at times definitely undesirable. It is therefore desirable to provide for a venting of the intercooler after complete unloading is effected,

and to maintain the same vented throughout the period of unloaded operation.

It is an object 0! my present invention to provide an improved compound compressor; It is another object of my invention to provide an improved compound compressor having improved unloading means. It is a further object of my invention to provide an improved controlling means for effecting the unloading of a compound compressor which will accomplish the functions pointed out as desirable in the foregoing analysis.

It is astill further object of my invention to provide an improved unloading means for a compound compressor in which a single discharge pressure responsive pilot valve is used to control fluid supply for unloading of both'the high and low pressure cylinders, and on which appropriate.

devices are further provided for effecting a delayed unloading of the high pressure cylinder,-

and, thereafter, throughout the period of unloaded operation, a venting oi the intercooler. Other objects and advantages of the invention will hereinafter more fully appear.

- In the accompanying drawing in which one illustrative embodiment which the invention may assume in practice has been shown,

Fig. 1 is a side elevatlonal view of a muJti-stage compressor in which the illustrative embodiment of the invention is incorporated,

v Fig. 2 is a vertical section on an enlarged scale through the secondary control device which gov- 5. erns the time of high pressure cylinder unloading and venting of the intercooler,

' Fig. 3 is a detail sectional view through the unloading apparatus associated with an inlet valve oi! a high pressure cylinder,

Fig. 4 is a section on the line 1-4 of Fig. 1 through the intake closure unloading apparatus, and

a Fig. 5 is a section with parts omitted on plane of the line 55 of Fig. 4.

I In the drawing, the compound compressor I"v has a frame 2, a driving shaft 3, a fly wheel 4, herein shownas belt driven, a low pressurecylinder 5, a high pressure cylinder 6, and an intercooler I: The low pressure cylinder 5 takes in 20 air through an air cleaner C andthrough an unloading mechanism generally designated 8 and of the total intake closure type, and discharges the air which it compresses, through a connection 9 to the intercooler 'I.- The air from the inter- 25 cooler is taken into the high pressure cylinder 6 through a connection ll, and after further compression is discharged through a discharge line I l. The intercooler is provided with a usual pressure the gage i2 and a pop safety valve II. The high 30.

pressure cylinder 6 is provided with inlet-valveopening, unloading mechanisms, of which one unit is shown in Fig. 3. The intake closure type unloading mechanism 8 includes a casing it, providing a space II to which-air passes initially. The intake space or the low pressure cylinder I I is connected with a space II, which is partitioned of! by the wall is having alined openings 2| and II, from the space l'|.- A double seat valve elemerit 22, normally held in open position by a 40 spring 23, is movable by a piston 24, reciprocable in a cylinder 25, to close the openings 20 and 2i, and thereby close communication between spaces is and I1 and efle'ct unloading of the low pressure cylinder by total closure of the intake to the latter. The cylinder 25 is placed in communication with a source of operating fluid and with exhaust through a connection 26. The high pressure cylinder is provided with inlet valves 28,

normally-held in closed position by springs 29 ed to actuate fingers 33 to open and maintain 5 open the inlet valves of the high pressure cylinder,

and connections 34 are arranged to eifect communication, between a source of pressure fluid supply and a point of exhaust, under the control of apparatus later described, and cylinders 35, in which the plungers 32 are reciprocable.

A pilot valve 36, which may be of any suitable type, and which is herein illustrated as a socalled RC pilot valve, is arranged to control comthe discharge line to said pipe; and, upon a pre-" determined drop in pressure below said predetermined maximum, to interrupt the communication previously established and vent the pipe 40 to atmosphere. A tee 4| connects the pipe 46 with the connection 26, previously described; and accordingly, on opening of the pilot valve 36 to establish communication between the compressor discharge passage H and the pipe 40, compressor discharge pressure passes immediately through the connection 26 to act upon the top of the plunger- 24 and to close the double beat valve 22, and thereby immediately unload the low pressure cylinder. From the T 4| another branch 42 passes to a valve mechanism generally designated 43. This last mentioned valve mechanism includes a casing 44 having a relatively large bore and an'alined smaller bore 46. Within these bores a composite piston 41 is reciprocable. The piston 41 comprises a larger portion 46 fitting the bore 45 and'a smaller-portion 46 fitting the bore 46. A suitable spring 50 constantly tends to maintain the composite piston 41 in raised position. The space below the piston portion 49 is'connected by a connection 5| to the air space in the intercooler, so thatthe lower end 01' the piston portion 48 is subjected to intercooler pressure. The upper end of the cylinder portion 45 communicates, through the connection 42 and the T 4|, with the passage 40, so that the upper end of the piston portion 49 is subjected to the diifer- 'ent pressures which prevail at different times in the passage 46. Upon a predetermined down- .ward movement of the piston portion 49 in the bore 46, the top end of the piston portion 49 uncovers a lateral opening 53, which is connected through a pipe 54 with the connections 34 leading to the inlet valve opening plungers 32 for the high pressure cylinder. The upper end 01' the space within the larger cylinder bore 45 is vented to atmosphere through an opening 55, and upon downward movement of the piston portion 48 through a predetermined distance in cylinder 45, the upper end of the portion 48 uncovers the mouth of a passage 56 which is connected by a pipe 51 with the pipe 5| which opens into the air space of the intercooler. It will therefore be evident that upon predetermined downward movement of the composite piston struc- Jture 41, the intercooler air spaces will be con- Obviously, since establishment of compassage mouth 56 slightly less than the distance of composite piston travel necessary to uncover the port 53.

It will be evident that the delay in downward movement of the composite piston structure 4! after unloading of the low pressure cylinder, can be controlled to efiect substantially any desired reduction in intercooler pressure before highpressure cylinder unloading 'and venting of the intercooler takes place. Desirable results can be obtained for a compressor having, during running, an intercooler pressure of about thirty pounds and a high pressure discharge line pressure of perhaps or pounds, if high pressure cylinder unloading andintercooler venting are caused to take place when the intercooler pressure is reduced to about 10 pounds. Obviously, the stiifness of the spring 50 will enter into the design of the apparatus, and it will be noted that I have shown about a 9 to 1 area ratio between the bottom surface of the piston portion 48, subjected to intercooler pressure, and the top pressure area of the piston portion 49. This would involve the use of a spring 50 exerting a relatively light pressure, and be suitable for about a 100# discharge pressure.

Because the upper end of the piston portion 49 might tend to entrap some air in thepipe 54 and I branches 34, and above the plungers 32, suitable means is provided to effect connection of the port 53 to atmosphere when the composite piston member 41 is in topmost position. Various means for accomplishing this result may be used, but I prefer to provide a peripheral groove 58 in the piston portion 49 at such a position that it will be opposite the port 53 when the piston portion 49 is in top position, and to connect the groove 58 by means of a suitable passage 59 with the space in the bore 45 above the piston portion 48, and so to atmosphere through the port 55. As a result of this arrangement, 53 will be connected to atmosphere whenever the composite piston structure is in uppermost position, but this connection will be discontinued before the top of the piston portion 49, upon downward movement, establishes communication between the r port 53 and the connection 42. Obviously, other means for the same purpose could be used, and if desired a bleed port could be placed in the connection 54 and make modification of the composite piston structure unnecessary.

The mode of operation of the apparatus described and illustrated will be readily understood from what has been said. During normal operation of the compressor, that is, with the pressure below the predetermined maximum desired, the pilot valve 35 will be in such position that the space above the plungers 32 will remain at atmospheric pressure. Communication between port 53 and passage 42 will be interrupted by the upper end of piston portion 49, and port 53 will be connected to atmosphere through groove 53, passage 59, cylinder bore 45 and passage 55.

Now starting with plungers 24 and 32 in raised position and with the composite piston 41 also in raised position and held there by the intercooler pressure acting on the larger areaat the bottom of the piston portion 48, it will be noted that when the predetermined desired maximum compressor discharge pressure is reached, the pilot valve 36 will connect the passage 4|] with compressor discharge line i l, and fluid will flow directly to the. line 26 and therethrough to the plunger 24 and close the compressor intake controlling valve 22.

- the high pressure cylinder will continue to pump,

and will pump down the intercooler pressure. When the intercooler pressure has been sufllciently reduced, the discharge line pressure acting on the upper end of piston portion 49 will overcome the effect of the much-reduced intercooler pressure on the bottom of piston portion 48, and force down the composite piston 41, and vent the remaining intercooler pressure through line 5|, 51, mouth 56, cylinder portion 45 and passage 55; and discharge line pressure then delivered through the passage 54 will unload the high pressure cylinder and the compressor willgoperate'fully unloaded. It will be noted that venting of the intercooler will merely make more positive the maintenance in lower position of the composite piston structure 41. When the pilot valve 35, upon a predetermined fall in compressor discharge line pressure, vents the line 40, both the low pressure cylinder' and the high pressure cylinder unloading-effecting plungers will be forthwith vented to the atmosphere through the pilot valve. The low pressure cylinder will immediately begin to pump into the intercooler, and the high pressure cylinder to pump out of the intercooler. Themouth 56 and the passage 55 have relatively small areas, and accordingly, there wil be no serious-retardation in the building up of intercooler pressure. When intercooler pressure builds up sufliciently, composite piston structure 41 will seal the mouth 56, close of! opening 53, and move to top position. Kiiy residual pressure in passage54 will be bled of! through groove 58, passage 59 and port 55..

From the foregoing description, it will be obvi-, ous that I have provided an in-fproved apparatus for controlling a compound compressor, which automatically provides for the utilization of most of the pressure contained in the intercooler at the instant unloading commences, whichprevents the building up of pressure in the intercooler during unloaded operation, which is effective to provide the desired results with extremely simple apparatus, and which requires only a single compressor discharge pressure responsive primary pilot valve,

and whose parts are simple, rugged and free from all danger of derangement in normal use. The apparatus is obviously susceptible of modification without departing from theiundamental spirit of the invention.

While I have in this application specifically described one form which my invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing 'from its spirit or the scope of the appended claims.

What I claim as new and desire to. secure by Letters Patentuisr 1. In combination, a compressor havinghigh and low pressure cylinders, means for unlo ading the low pressure cylinder, and automatically acting means controlled by variations in pressure,

at a point beyond said unloading means, arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the low pressure cylinder discharge freely to atmosphere at a point short of said high pressure cylinder.

2. In combination, a compressor having high and low pressure cylinders, intake closure means for unloading the low pressure cylinder, and automatically acting means controlled by variations in pressure, at a point beyond said unloading means, arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder 'and venting the low pressure cylinder discharge freely to atmosphere at a point short of the high pressure, cylinder.

3. In combination, a compressor having high and low presure cylinders, means for unloading the low pressure cylinder, and automatically acting means operated by terminal pressure and governed by variations in pressure, at a point beyond said unloading means, arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the low pressure cylinder discharge freely to atmosphere.

4. In combination, a compressor having. high and low pressure cylinders, intake closure means for unloading the low pressure cylinder, and

automatically acting means operated by terminal pressure and governed by variations in pressure, at a point beyond said unloading means, arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and. venting the low pressure cylinder discharge freely to atmosphere.

5. In combination, a compressor having high and low pressure cylinders and an intercooler, means'for unloading the low pressure cylinder,

and automatically acting means operated by terminal pressure and opposed in its movements by intercooler pressure andgoverned by variations in pressure arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the intercooler freely to atmosphere.

6. In combination, a compressor having high and low pressure cylinders and an intercooler, in-

take closure means. for unloading the low pressure cylinder, and automatically acting means operatedby terminal pressure and opposed in its movements by intercooler pressure and governed by variations in pressure arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the intercooler freely to atmosphere.

7. In combination, a compressor having, high and low pressure cylinders and an intercooler, intake closure means for unloading the low pressure cylinder, inlet valve opening means for unloading the high pressure-cylinder, and automatically acting means controlled by variations in pressure arising fromv the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the inter cooler freely to atmosphere.

8. In combination, a compressor having high and low pressure cylinders andan intercooler, in-

-and responsive to variations in pressure arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the intercooler freely to atmosphere.

9. In combination, a compressor having high and low pressure cylinders and an intercooler, intake closure means for unloading the low pressure cylinder, inlet valve opening means for unloading the high pressure cylinder, and automatically acting means controlled by variations in pressure in the intercooler arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder and venting the intercooler freely to atmosphere.

10. In combination, a compressor having high and low pressure cylinders and an intercooler, intake closure means for unloading the low pressure cylinder, inlet'valve, opening means for unloading the high pressure cylinder, and automatically acting means operated by terminal pressure and responsive to variations in pressure in the intercooler arising from the unloading of the low pressure cylinder for subsequently unloading the high pressure cylinder'and just prior thereto venting the intercooler to atmosphere.

11. In a controlling apparatus of the type defined and adapted to effect supply oi. pressure to a high pressure cylinder unloading means and to vent an intercooler, a casing providing alined cylinder bores of difierent diameters, a composite piston having portions fitting said bores, intercooler vent means controlled by the larger piston portion, high pressure cylinder unloading means, a supply port for said high pressure cylinder unloading means controlled by the smaller piston portion, means for subjecting the smaller piston portion to a pressure to be controlled, and means for applying an opposing pressure on the larger piston portion.

12. In a controlling apparatus of the type defined and adapted to effect supply or pressure to a high pressure cylinder unloading means and to vent an intercooler, a casing providing alined cylinder bores of different diameters, a composite piston having portions fitting said bores, intercooler vent means controlled by the larger piston portion, high pressure cylinder'unloading means, a supply port for said high' pressure cylinder unloading means controlled by the smaller piston portion, means tor subjecting the smaller piston portion to the compressor discharge pressure 'to be controlled, and means for applying as an opposing pressure intercooler pressure on the larger piston portion.

13. In a controlling apparatus of the type dec fined, a casing providing alined cylinder bores of diiIerent diameters, the larger bore vented at its top, a composite piston having portions fitting said bores, a. port controlled by the larger pis ton portion, a port controlled by the smaller piston portion, means for subjecting the smaller piston portion to a pressure to be controlled, and means for applying an opposing, lower, related pressure on the larger piston portion and conducting the last named pressure to the first mentioned port.

15. In combination, a compressor having high variations in pressure arising from the unloading of the low pressure cylinder for subsequently venting the'inter-cooler to atmosphere and then unloading the high pressure cylinder.

16. In combination, a compressor having high and low pressure cylinders and an intercooler, intake closure means for unloading the low pressure, cylinder, and automatically acting means controlled by variations in pressure arising from the unloading of the low pressure cylinder 'for subsequently venting the intercooler to atmosphere and then unloading the high pressure cylinder.

1'7. In a controlling apparatus ofthe type defined and adapted to effect supply of pressure to a high pressure cylinder unloading means and to vent an intercooler, pressure responsive valve means movable in one direction to efiect intercooler venting and to admit pressure to eflect high pressure cylinder unloading, and in an opposite direction to.stop intercooler venting and effect high pressure-cylinder re-loading, and controlling means for said valve means having opposed surfaces of unequal areas, the smaller subjected to high pressure cylinder discharge pressure and the larger to intercooler pressure.

18. In a controlling apparatus or the type defined and adapted to effect supply of pressure to a high pressure cylinder unloading means and to vent an intercooler, pressure responsive valve means movable in one-direction to effect intercooler venting and to admit pressure to effect the smaller subjected to high pressure cylinder discharge pressure and the larger to intercooler pressure.

19. In a controlling apparatus of the type defined and adapted to efiectsupply of pressure to a high pressure cylinder unloading means and to vent an intercooler, pressure responsive valve means movable in-one direction to efiect intercooler venting and to admit pressure to effect high pressure cylinder unloading, and in an opposite direction to stop intercooler venting and eflect high pressure cylinder re-loading, and controlling means for said valve means having opposed surfaces of unequal areas, the smaller subjected to a pressure to be controlled and the larger to a related lower pressure.

20. In a; controlling apparatus or the type defined and adapted to efiect supply of pressure to a high pressure cylinder unloading means and to vent an intercooler, pressure responsive valve means movable in one direction to eii'ect intercopier venting and to admit pressure to eii'ect high pressure cylinder unloading in the order named, and m an opposite direction to stop inter cooler venting and effect high pressure cylinder re-loading, and controlling means for said valve 76 sure unloading means for efl'ecting delayed un-.'

ance with compressorQdischitrgI: pressure variations, first unloading said low pressure cylinder, and thereafter unloading said high pressure cylinder and venting the ioyr pressure cylinder dis!- charge freely to atmosphere, and eilecting reloading or the low and high pressure cylinders simultaneously upon reduction oi, compressor discharse pressure to the desiretl minimum. said means in cluding means automatically controlled by vari ations in pressure at a-polnt' beyond the low presloading, of said high pressure cylinder and venting otthe low pressure cylinder discharge.

22. The combination deilnedin claim 21 in which means for eiiecting unloading of the low pressure cylinder is provided in the form of intake closure means.

23 The. combination defined in claim 21 in whch the means for effecting delayed unloadin of the high pressure cylinder is controlled by intercooler pressure. I

24. The combination defined in claim 21 in which the means for effecting delayed unloading oi the high pressure cylinder is operated by compressor discharge pressure.

ALEXANDER D. FERGUSON. 

